A Low-Noise PFM-Controlled Buck Converter for Low-Power Applications

APFM-controlled buck converter with discrete frequency hopping is proposed. The converter employs two uniquely related switching frequencies to fully spread the converter´s output switching noise without generating additional tones at any of the switching frequencies. The peaking in the noise floor resulting from spreading the switching noise is reduced by using up to eight switching frequencies. The converter is implemented in 0.35 μm standard CMOS technology and occupies 0.29 mm². With a spur-free output spectrum and low noise floor peaking, the proposed converter is ideal for low-current noise-sensitive loads such as analog and RF circuit loads in portable communication devices.